In pea plants, the long-stem trait (L) is dominant and the short-stern trait (I) is recessive. Two pea plants were crossed, producing seeds that yielded 165 long-stem plants and 54 short-stem plants. The genotypes of the parent plants were most likely
LI and LL
LI and LI
II and II
LL and II
Correct answer: (b)
The ratio of long stem plants to short stem plants among the progeny is 165:54 which means it has a ratio of 3:1. This ratio is possible if the parents are heterozygous in nature which after the cross will produce homozygous tall, heterozygous tall and homozygous dwarf offsprings.
As the heterozygous offspring expresses the dominant allele, they will also be tall. This is a classic example of the monohybrid ratio that produces a ratio of 3:1 in the F2 generation of pure line parents.